In December 2024, New York City enacted Local Laws 126 and 127 alongside the City of Yes for Housing Opportunity zoning text amendment — a major step toward making ADUs (Accessory Dwelling Units) possible in one- and two-family homes.
These changes open the door for homeowners to safely add new housing in attics, basements, cellars, garages, or detached backyard structures, expanding flexibility for multigenerational living or rental income.
What the New Laws Do
Local Law 126
- Creates a path to legalize existing basement and cellar apartments that were previously unlawful.
- Establishes a 10-year compliance program with milestones and safety upgrades.
Local Law 127
- Provides a clear framework for zoning, construction, fire safety, and occupancy requirements so new ADUs are built safely and legally.
Together, these laws give homeowners certainty — and give the City more housing options.
General Requirements for ADUs
- One ADU per Lot – Applies to one- and two-family homes.
- Owner Occupancy Required – You must live on the same lot.
- Maximum Size – Up to 800 sq. ft. of zoning floor area.
- Separate Entrance – Must have its own private entrance.
- Fire Safety – Adding an ADU to a two-family home may trigger Multiple Dwelling Law requirements (e.g., fire walls).
- Legalization Program – Pre-existing basement/cellar units must follow Building Code Appendix U and pass safety milestones.
Exceptions & Restrictions
- Backyard ADUs: Prohibited in Historic Districts, R1-2A, R2A, and R3A districts outside the Greater Transit Zone, and the Special Bay Ridge District.
- Subgrade ADUs: Not allowed in FEMA flood zones or DEP 10-year flood-risk areas.
- Legalization Areas: LL126 applies only to certain community districts in the Bronx, Brooklyn, Manhattan, and Queens.
Types of NYC ADUs
- Detached Backyard Units – Free-standing “tiny homes” with private entrances.
- Attached In-Law Suites – Additions with independent access.
- Basement or Attic Conversions – Strict fire/egress rules apply.
- Garage Conversions – Often allowed even where backyard ADUs are restricted.
Financial Incentives
New York State’s Plus One ADU Grant Program offers up to $125,000 per homeowner for design, permitting, and construction. This can significantly offset upfront costs and make your project more feasible.
FAQs
When can I apply?
Applications will open once DOB and DEP finalize rules — start your design now to be ready.
Who is eligible?
Owner-occupants of one- or two-family lots, subject to zoning and flood restrictions.
Can I legalize my existing basement unit?
Yes, if it existed before April 20, 2024, is in a program area, and meets compliance milestones.
Are backyard ADUs allowed everywhere?
No — they’re restricted in some zones and historic districts, though garage conversions may still be possible.
What’s the max size?
ADUs can be up to 800 sq. ft.
From Complexity to Confidence
NYC’s “City of Yes” represents one of the most significant opportunities for homeowners in decades — but getting it right means understanding zoning, fire codes, and permitting.
At Dwelly, we believe good design and clear guidance turn regulations into possibilities. If you’re in NYC, now is the time to start planning so your ADU is ready to go when applications open.
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